1. The Field of the Invention
The present invention relates to portable furniture and, more particularly, to novel systems and methods for providing comfortable, compact, inexpensive, and lightweight seating for easy transportation and storage.
2. The Relevant Technology
Throughout history, people have sought more comfortable seating arrangements. Chairs, stools, and the like allow people to relieve stress on the legs and feet, while remaining alert and performing tasks: that do not require a great deal of motion. In the twentieth century, folding chairs have made it possible for people to keep a space clear when necessary, and to erect suitable seating for gatherings or special events. However, current folding chairs possess a number of drawbacks.
For example, folding chairs are often somewhat heavy. The chair must reliably support the weight of even a fairly large person. The bending stress on any member is proportional to the length of the member multiplied by the force acting upon it. Therefore, the length of the seat effectively multiplies the forces tending to bend or break the seat. Typically, seats for folding chairs have been made from stronger (and heavier) materials, such as steel, to overcome the effect of these bending stresses. The resulting chairs are heavier and therefore cost more to ship, and require more effort to move, fold, and unfold.
Thus, it is desirable to use lightweight materials such as plastics to reduce the weight of folding chairs. However, many known folding chairs, especially those that incorporate lightweight materials, do not stand up to repetitive use. Groups such as the Business and Institutional Furniture Manufacturers"" Association (B.I.F.M.A.), have set up standards for portable furniture. Such standards typically require that portable chairs be designed to receive a given weight loading to simulate use for a specified number of cycles, often on the order of 100,000. Many known folding chairs bend or break after only a few thousand cycles, and therefore can be expected to have a relatively short useful life.
Certain known chairs use metal to reinforce lightweight materials. The seat may, for example, be supported by a frame encircling the seat or by metal rods threaded through the lightweight material. In addition to increasing the weight of the folding chair, such reinforcing measures add to manufacturing time because the supporting structure must be properly aligned with the seat, and possibly with the legs as well.
In general, many known folding chairs are somewhat expensive to produce because the manner in which they are assembled requires the use of a great deal of manual labor. The legs must often be properly aligned with the seat so that mechanical fasteners can be attached to the legs and the seat. If metal supporting parts are to be threaded through the lightweight seat member to connect the legs, the lightweight seat member may have to be aligned with each leg assembly so that the threading operation can be carried out. Often, the various fasteners involved must be installed at locations that are not easily accessible for machinery. Thus, the fasteners must often be installed by hand.
Accordingly, a need exists for a portable, folding chair that is lightweight and comfortable, and yet folds to a thin, stackable configuration. Such a chair must safely support the weight of a fairly heavy person. In addition, the chair should be inexpensive to produce in large quantities with a minimum of parts and assembly.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available folding chairs. Thus, it is an overall objective of the present invention to provide an inexpensive, lightweight, comfortable, chair capable of folding to fit within a small volume.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein in the preferred embodiment, a folding chair with an interference fit support bracket is provided. According to selected embodiments, the folding chair may comprise a pair of symmetrical leg assemblies, each of which includes a front leg and a rear leg. Each of the legs may have a lower end in contact with the ground or floor, and an upper end extending upward from the lower end. A seat may be suspended between the leg assemblies. The upper end of the front legs may also be extended to retain a backrest between the leg assemblies.
The seat may be pivotally attached to the front leg and the rear leg of each of the leg assemblies. Each of the leg assemblies may also have a strut pivotally attached to the front leg and the rear leg, so that the strut, front leg, rear leg, and seat form a four-bar, four-pivot linkage. The chair may thus be folded by rotating the seat with respect to the front legs, so that the seat and rear legs fold into a position substantially parallel to the front legs.
The seat may comprise a lightweight seat member constructed of a lightweight material, such as plastic, and a pair of support brackets constructed of a stronger material such as a metal. The lightweight seat member may be hollow and may be formed through a suitable process such as injection or blow molding. Each support bracket may be elongated in the longitudinal direction, with a generally enclosing cross-sectional shape designed to grip the lightweight seat member to restrict relative motion of the support bracket and lightweight seat member perpendicular to the length of the support bracket. The lightweight seat member may, in turn, have engaging features such as a lateral ridge and a slot to receive each bracket. The lightweight seat member may be generally configured to make contact with each of the support brackets in several places so that lateral and transverse relative motion of the lightweight seat member and support brackets can be fully prevented.
Each support bracket preferably grips the seat with a retention force sufficient to ensure that the support bracket cannot slide relative to the lightweight seat member in the longitudinal direction during normal use of the folding chair. To install the support brackets on the lightweight seat member, each support bracket is preferably aligned with the corresponding engaging features of the lightweight seat member and pressed with an installation force similar in magnitude to the retention force.
Each support bracket may also have a tab designed to be bent into engagement with a corresponding tab engagement slot formed in the lightweight seat member after the support bracket has been properly positioned with respect to the lightweight seat member. The tabs operate in conjunction with the retention force of the support bracket to ensure that the brackets cannot slide longitudinally off of the seat.
The folding chair may be easily assembled by, first, assembling the leg assemblies, and then affixing a support bracket to each leg assembly through the use of mechanical fasteners such as rivets, bolts, shafts with locking pins, or the like. The backrest may be affixed to the legs by any suitable fastening mechanism. The leg assemblies may then be aligned relative to each other to receive the lightweight seat member, and the lightweight seat member may be pressed into engagement with the brackets.
Thus, the folding chair of the present invention provides a number of unique advantages over the prior art. For example, a minimum of metal material may be used to affix the lightweight seat member to the leg assemblies. No metal supports, such as rods or backing plates, need be affixed to or threaded through the lightweight seat member. Additionally, fixation is accomplished without forming holes in the lightweight seat member; thus, there are no stress concentrations to weaken the seat under repeated use. The folding chair can be easily assembled with actions that can generally be performed rapidly by machine.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.